<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>CSS控制表单样式</title>
<link href="style.css" type="text/css" rel="stylesheet" />
</head>
<body>
<form action="#" method="post">	
  <p>
    <span>账号：</span>
    <input type="text" name="username" class="num" pattern="^[a-zA-Z][a-zA-Z0-9_]{4,15}$" />
  </p>
  <p>
    <span>密码：</span>
    <input type="password" name="pwd" class="pass" pattern="^[a-zA-Z]\w{5,17}$"/>
  </p>
  <p>
    <input type="button" class="btn01" value="登录"/>
  </p>
</form>
</body>
</html>